The current invention is related to electrical power cell isolation, and in particular to a system and method for bypassing and isolating a malfunctioning electrical power cell.
Electrical power systems often consist of several electrical power cells connected in series to provide larger voltages than a single cell can produce. In a system such as this, if a cell malfunctions, the cell can create high impedance and essentially disable the entire string of electrical power cells. Critical systems, such as those in space, require continuous operation and cannot be disabled whenever a single electrical power cell malfunctions.
For systems that require continuous operation, it is essential to have the ability to isolate and bypass a malfunctioning electrical power cell. To provide continuous operation, and not cause any damage to the system, the circuit must be able to provide a continuous path for current flow in the event of an electrical power cell malfunction. If a switch is used to isolate and bypass a malfunctioning electrical power cell, the circuit must have the ability to prevent a large voltage spike created by high impedance during throw time of the switch.
Prior circuits provided diodes in parallel with the electrical power cells so that when the electrical power cell malfunctioned, and created a high impedance, current would flow through the diode, bypassing the malfunctioning cell. This setup allowed for uninterrupted current flow, but created excessive power loss through the diode as the diode provided a continuous conduction path with high power dissipation.
Other bypass circuits utilized a more costly approach involving switches in conjunction with diodes and a fuse. When the electrical power cell malfunctioned, the diodes would allow current to flow through the fuse, tripping the fuse, and activating a switch to bypass the damaged cell. Because the switch was thrown by blowing a fuse, the act of setting the switch was irreversible. The only way to reactivate the cell was to replace the switching mechanism.